38 NEW YORK STATE MUSEUM 
weather enables wheat, barley and rye to grow luxuriantly. Dur- 
ing midsummer, as a rule, only a little volunteer wheat is in a con- 
dition for the larvae to live on, though this was very different with 
barley in rg01, when continued moist weather, after the spring 
brood had developed to pupae, brought out hosts of flies. Eggs 
were laid in large numbers in the barley, especially the late sown, 
and in early July many fields in Genesee county were badly infested. 
The maggots were near the ground in the latest barley, and in that 
early sown occurred 10 to 12 inches above the surface, showing 
that the insect lives by preference in soft growth and inferentially 
that it thrives only indifferently in the older, harder growth. The 
relation between a rank, succulent growth and injury was further 
shown in a hilly patch of wheat. The grain on the gravelly, com- 
paratively dry knolls was nearly immune, while in the more moist 
gullies the stalks of wheat were very scattered. The resistance of 
so-called “ fly proof” wheats depends in large measure upon the 
relative hardness or maturity of the stalks at the time the flies 
appear and deposit eggs. 
Emergence of flies. This is an exceedingly important matter 
because successful methods of preventing injury depend upon a 
correct understanding of the habits of the flies. The flight of the 
Hessian fly is dependent on weather conditions. The following 
rules will assist materially in forecasting probabilities : 
1 The flies may remain an indefinite period in the * flaxseed ”’ 
or pupal stage during dry weather. . 
2 “ Flaxseeds ” or pupae are very likely to develop flies in large 
numbers during damp, warm weather. 
3 Adults are killed by heavy frosts though this is not true of 
larvae and “ flaxseeds”” or pupae, and hence flies may appear and 
deposit eggs between killing frosts. 
4 Under certain conditions some of these insects may spend 
nearly a year in the flaxseed stage. 
5 Recently emerged flies must, in all probability, deposit eggs 
shortly upon succulent grain. 
The above rules show that egg-depositing flies may appear at 
any time during the growing season, provided weather conditions 
are favorable, though naturally we would expect them to issue in 
large numbers only at the first favorable period after a large brood 
had attained the “ flaxseed” or pupal stage. Thus, as our springs 
are usually warm and moist, this means that ordinarily most of 
the flies will emerge the latter part of April or early May. Then 
